Raman Enhancement in Metal-Cladding Waveguide and the Influence of the Metal Film Surface Roughness

Enhanced Raman scattering in a metal cladding waveguide was demonstrated theoretically and experimentally. The thickness of guiding layer of the waveguide sensor was about 0.5-1 mm, the analyte was located in the guiding layer of the sensor, where the electric field intensity is enhanced owing to the ultrahigh order modes excited by a focused laser beam. An enhancement of at least one order of magnitude was got experimentally. As the coupling metal film is only about 30 nm, the effect of surface roughness may not be ignored. The effect of surface roughness of coupling film on Raman scattering was also studied. It was found that roughness of coupling film surface may also make a contribution to Raman enhancement.